New results from the lattice on the theoretical inputs to the hadronic tau determination of V_us

TL;DR

This paper uses lattice data to evaluate the accuracy of the Operator Product Expansion in determining |V_us| from tau decay data, addressing discrepancies with unitarity and kaon decay results.

Contribution

It introduces lattice-based assessments of the OPE's reliability in flavor-breaking correlator analyses for tau decays, proposing an alternative correlator to improve convergence.

Findings

Lattice data suggests potential issues with the OPE representation in current analyses.

An alternative correlator reduces convergence problems in sum rule evaluations.

Preliminary results inform future refinements of |V_us| determinations.

Abstract

Recent sum rule determinations of |V_us|, employing flavor-breaking combinations of hadronic tau decay data, are significantly lower than either expectations based on 3-family unitarity or determinations from K_ell3 and Gamma[K_mu2]/Gamma[pi_mu2]. We use lattice data to investigate the accuracy/reliability of the OPE representation of the flavor-breaking correlator combination entering the tau decay analyses. The behavior of an alternate correlator combination, constructed to reduce problems associated with the slow convergence of the D = 2 OPE series, and entering an alternate sum rule requiring both electroproduction cross-section and hadronic tau decay data, is also investigated. Preliminary updates of both analyses, with the lessons learned from the lattice data in mind, are also presented.